Immediate processing was canceled

What causes this issue?

The IDoc is supposed to be immediately transferred to the application
for processing.
An error has occurred as described below:
Immediate IDoc inbound processing should occur using the server group '
&v1&'.
However, using this server group results in the exception
communication_failure or system_failure.
The following error message is displayed:
&v2&&v3&

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Use report RBDAPP01 to transfer the IDocs to the application.

Procedure for System Administrators

Find the detailed error description in the system log and, if possible,
eliminate the cause of the error.

Error message extract from SAP system. Copyright SAP SE.